WASHINGTON • Key US senators John McCain and Marco Rubio won their Republican primaries, setting up high-profile re-election efforts in November as their party fights to retain control of Congress.
A freshman lawmaker, Mr Rubio of Florida easily defeated business executive Carlos Beruff, securing around 72 per cent of the vote.
The closely watched Florida match-up is considered to be among those that could tip the Republican-controlled Senate into Democratic hands in November, especially if presidential hopeful Donald Trump underperforms in the general election and drags down other Republicans on the ballot.
Mr Rubio, 45, will face a general election race against Representative Patrick Murphy, 33, a two- term Democrat.
Mr McCain of Arizona, a veteran senator seeking a sixth term, could also face a serious challenge from Representative Ann Kirkpatrick, 66, who has made a point of courting Latinos and American Indians in an increasingly diverse and competitive state.
About a third of the 100-member Senate and the entire House of Representatives are up for grabs in November.
Mr Rubio was a rising Republican star whose presidential bid fizzled in March after he was thrashed by Mr Trump in the Florida primary.
Mr Rubio had pledged to return to private life, but reversed course and launched his Senate re-election bid, scaring nearly every challenger out of what had been a crowded Republican field.
He called it "an unusual road back" to the Senate.
"But I just couldn't be at peace with the idea that we were going to not just potentially lose the Senate seat but lose the balance of power in the Senate at this critical moment in our nation's history," he told supporters after claiming victory following Tuesday's vote.
Mr McCain was projected to handily win his contest against a more conservative candidate and advance to the November election.
"This one has a ways to go yet, and it's not going to get any easier," he said in a victory speech.
Although his rival Kelli Ward, a former state senator, is an avid Trump supporter, the Republican nominee eventually backed Mr McCain's re-election bid, depriving Dr Ward of much-needed political oxygen to mount a successful challenge.
Dr Ward, 47, had argued that Mr McCain, who turned 80 on Monday, had grown too old and "weak" to serve another six-year term.
Mr McCain, the 2008 Republican presidential nominee, has spent three decades in the Senate. He was seen as one of the senators most vulnerable to a challenge by the far right, but ultimately prevailed easily.
AGENCE FRANCE-PRESSE, NEW YORK TIMES
