(Bloomberg) - Donald Trump slammed Republican rivals and party leaders seeking to bleed him of delegates on Tuesday (March 8) as the presidential race moved to Michigan in the industrial Midwest, a crucial test of his appeal to disaffected voters and whether efforts to stop him are working.

Republicans also are holding primaries in Mississippi and Idaho and caucuses in Hawaii. Democratic front-runner Hillary Clinton, meanwhile, will seek to expand her delegate lead in primaries in Mississippi and Michigan, where Bernie Sanders is trying to slow her march to the nomination.

"Four years ago, they were dying, the Republicans, and now it's been energised," Trump said Tuesday (March 8) on MSNBC, according to a transcript.

Instead of being grateful to him for spurring voter turnout, Trump said, "they take ads against me."

In the closing hours of the latest day of nomination contests, Trump faced sharp attacks from his strongest opponent, Texas Senator Ted Cruz, who ripped the billionaire's decision to ask supporters to pledge to vote for him.

"The idea that a candidate running for office wants people to pledge loyalty to him like subjects to a king?," Cruz said to reporters in Raleigh, North Carolina. "Well, we've have seven years of a president who thinks he's an emperor."

The Texas senator said that Trump's responses to national security questions at the debates suggest he lacks the "experience" and "knowledge to be commander in chief."

Cruz also countered Trump's claim that Cruz touts the Bible in one hand and then lies. "Typically, when he goes down to attacking people's faith it's a sign that Donald is really, really worried," Cruz said. "I understand the last election day - Super Saturday - was a very bad day for Donald.... He got clobbered."

Trump suffered a split decision Saturday, winning in Louisiana and Kentucky but losing caucuses in Kansas and Maine to Cruz.

Trump's victories also were narrower than polling had indicated, suggesting that attacks on his crude language and ill-defined policies from 2012 nominee Mitt Romney and others may be having an impact.

Meanwhile, Senator Marco Rubio's campaign attacked Cruz for playing "dirty tricks" in Hawaii, saying his campaign should not have spread a false report stating that "Marco Rubio's advisers are telling him to drop out of the presidential race before losing his home state of Florida in a few days time."

"Senator Cruz is up to his dirty tricks again spreading false rumors and lies," Rubio campaign spokesman Joe Poender said in a statement. "We won't allow him to do to Marco Rubio in Florida what he did to Ben Carson in Iowa."

Romney Robocalls Romney recorded a phone message to voters urging them not to vote for Trump, which Ohio Governor John Kasich'scampaign said it is sending to Michigan primary voters.

"If we Republicans were to choose Donald Trump as our nominee, the prospects for a safe and prosperous future would be greatly diminished," Romney said on the call.

"It's his words, I don't write his scripts," Kasich said. "We want to make sure the people don't think that Romney's for somebody else and not for me, particularly in the state of Michigan."

The results for Kasich will be closely watched because he has staked his presidential campaign on winning his home state, and Michigan's industrial base and working-class roots bear similarities to the Buckeye State.

"I think we're on a roll," Kasich said in Lansing, wearing a yellow tie that he said represented the sun "really coming up on the Kasich campaign." Rubio also sent a Romney message to voters, the Associated Press reported. Romney also offered his help to Cruz, Politico reported, citing an unidentified spokesperson for the former nominee.

Positioned to Win Trump spent Tuesday hammering Romney and Rubio in postings to his 6.7 million followers on Twitter. Trump has enjoyed double-digit leads in Michigan, thanks to his appeal to white, working-class voters. The contest there will show whether Cruz, Kasich or Rubio can claim any momentum as an alternative heading into key winner-take-all contests on March 15.

Trump is increasingly focused on Rubio, who's promised to win his home state of Florida and whose campaign shot down a CNN report Monday that he was being urged by advisers to drop out before March 15 to save face. A poll released by Florida TV stations on Tuesday showed Trump leading Rubio 42 percent to 22 percent.

In Michigan, Trump looks poised for a win, "but the race may be tightening in the final hours," Patrick Murray, director of the independent Monmouth University Polling Institute, said in a statement. "Trump's support may be dropping, while Kasich's star could be rising." Campaigning Monday in Michigan, Kasich said he thinks it's likely that no candidate will amass the 1,237 delegates needed for the nomination before the party's convention in Cleveland in July. He also said he doesn't think whoever has the lead in delegates should necessarily prevail there.

"To say, 'Well, you know, I have more than you, therefore I should get it?' Go out and earn it," Kasich told reporters after a town-hall meeting in Monroe, Michigan. "Don't be whining about how it's going to work. Go get what you need to be the legitimate winner." Strong Finish Kasich is betting that a strong finish in Michigan, followed by a victory a week later in Ohio with its 66 delegates, will prevent Trump from getting the needed delegates and start a new phase of the campaign. "Let us, for the rest of this day, leave no stone unturned, have the state of Michigan send a message and launch me into the state of Ohio, where we will have a whole new day in American politics," Kasich said in Lansing.

Trump is seeking to prevail in Ohio and defeat Rubio in Florida on March 15 to claim the 99 delegates there. Overall, Trump leads the delegate chase with 384, followed by Cruz with 300, Rubio at 151 and Kasich with 37, according to an Associated Press tally.

A RealClearPolitics average of polls in Michigan shows Trump leading with 37.3 percent, with Kasich in second at 25 percent and Cruz in third at 19.8 percent. Rubio, who had sought to separate himself as the establishment alternative to Trump, is last at 10 percent.

Kasich may have gotten a boost from his March 3 debate performance in Detroit, when he refused to engage in attacks on Trump by Rubio and Cruz, said David Dulio, chairman of the political science department at Oakland University in Rochester, Michigan. The Ohio governor also has devoted more time than any other candidate to Michigan, he said.

Union Members Trump appeals especially to the blue-collar voters in areas such as Macomb County north of Detroit, home of automotive plants and parts supplies and mostly white, union-member voters, said Stu Sandler, a Republican consultant from Ann Arbor who is not affiliated with any of the candidates. Those voters were the inspiration for the label "Reagan Democrats," who supported Republican Ronald Reagan in the 1980s.

Trump has held rallies in Macomb County and in Cadillac, emphasizing messages that resonate about the loss of jobs from trade deals and companies such as Ford Motor Co. building plants outside of the US, Sandler said.

"Donald Trump's campaign has fixed like a laser on working- class voters, and I think it's really paid off, and it's brought an influx of new voters into the Republican primaries," he said.

One measure of that impact could be the number of people who take a Republican ballot, Dulio said. Michigan has an open primary in which residents can vote in either party's primary, and as of Monday, 307,877 people had requested a Republican absentee ballot compared with 235,583 Democratic requests, according to the Michigan Secretary of State's office.

David Evans, 53, who works for General Motors, and his son, Travis, a 25 year-old college student and Air Force veteran, attended Kasich's event in Monroe on Monday and both said Trump appealed to them because he's a businessman and not a typical politician. But the father is considering Cruz and the son is backing Kasich because they are leery that Trump is "a wild- card," as Travis Evans put it.

"I like Trump, but I'm not sure I trust him," Dave Evans said.

Democrats' Ads While the Republican race is competitive, Michigan residents had been exposed to far more broadcast television advertising on the Democratic side through March 1, according to tracking data from Kantar Media's CMAG.

Sanders had run 3,178 spots in markets covering the state, compared to 2,663 for Clinton. On the Republican side, Kasich and Cruz were the only two candidates to run broadcast television spots, and at levels much lower than the Democrats, data show.

Clinton enjoys a lead of more than 20 percentage points in an average of recent polls by RealClearPolitics, even as Sanders has tried to link her to manufacturing jobs lost to trade deals that she supported. The Vermont senator doesn't seem to be getting any traction, said Susan Demas, publisher of Inside Michigan Politics, a newsletter in Lansing.

"You would think that it would be a fertile issue in Michigan," Demas said. "But it seems that Democrats are willing to give Clinton a pass on it." Clinton also appears to be connecting with black voters in Michigan the way she did in previous contests in the South. Demas said polling after the Iowa caucuses showed the former secretary was winning 82 percent of blacks in the state.

Clinton aggressively went after Sanders in a televised debate in Flint on Sunday for opposing the US$700 billion bank bailout in the 2008 financial crisis, saying it had cleared the way for the US$82 billion auto industry bailout key to Michigan workers.

According to an Associated Press tally, Clinton has a delegate lead over Sanders of 1,130 to 499, including superdelegates, elected officials and party leaders who are free to change their allegiances. It takes 2,383 delegates to clinch the Democratic nomination.