WASHINGTON - Republican voters' embrace of fringe and divisive candidates is jeopardizing the party's goal of taking control of the U.S. Senate in November's midterm elections, as well as winning key governors' races.

Far-right candidates who have echoed former President Donald Trump's spurious stolen-election claims could win primaries in Arizona and Michigan on Tuesday, likely boosting the odds of Democratic victories in those battleground states this fall.

In Arizona, polls show Trump-backed candidates Blake Masters and Kari Lake leading the Republican fields for Senate and governor, respectively. A far-right candidate, Tudor Dixon, could capture the party's nomination for governor in Michigan. She was endorsed by Trump late on Friday.

With Democratic President Joe Biden deeply unpopular among voters and an inflation-ravaged economy, political analysts and strategists say Republicans appear poised to assume control of the U.S. House of Representatives and have a strong chance of reversing Democrats' narrow Senate majority. Taking either would allow them to kneecap Biden's legislative agenda.

The battle for the Senate has become more complicated, however. Republican nominees in competitive races in Georgia, Ohio and Pennsylvania are first-time candidates who have raised far less than their Democratic opponents and have struggled to broaden their appeal beyond Trump's fervent, but narrow, base of support.

Democrats, meantime, have become more energized in recent months by the Supreme Court decision overturning the Roe v. Wade ruling that recognized women's constitutional right to abortion and the ongoing hearings on the Jan. 6, 2021, insurrection.

With the Senate divided 50-50, Republicans need to pick up a net total of just one seat to gain control.

Jacob Rubashkin, an analyst with Inside Elections in Washington, said Republicans remain favored to take the Senate, but it is no longer the slam-dunk it once appeared to be.

"Republicans are certainly creating opportunities for Democrats in Senate races," he said, "but I think it's too early to declare that they're snatching defeat from the jaws of victory."

FiveThirtyEight, an influential political analysis website, this week declared the race for the Senate to be a "toss-up" and gave Democrats the edge.

CRISIS AVERTED?

Republicans may have headed off a potential tough fight to keep a seat in Missouri, which also has a primary on Tuesday.

Senate candidate Eric Greitens, a former governor who has been accused of domestic abuse by his ex-wife, appears to be falling back in the Republican field after a party-funded super PAC blanketed the airwaves with the allegations in the hope of derailing his campaign.

James Harris, a Republican political strategist in Missouri, said Greitens' candidacy should serve as a warning to his party that it cannot take winning Congress for granted given the more galvanized Democratic electorate.

"A lot has changed in the last two months," Harris said. "So if Republicans go into Senate races with weak candidates like Eric Greitens, they're going to be expensive races that we might lose."

One of those Senate races may well be in Arizona, where Democratic Senator Mark Kelly has amassed a large war chest while Republicans have engaged in a bitter primary. Kelly would go into a race against Masters as the favorite, according to early polls.

Masters, a venture capitalist making his first political bid, has echoed Trump's election-fraud claims and earlier this month cast doubt on the legitimacy of this year's midterm elections.

At a rally led by Trump in Arizona last week, Masters pledged to work to impeach Biden and prosecute Dr. Anthony Fauci, the U.S. government's top COVID-19 expert.

If elected, Masters said he "would finish the work that President Trump got started."

A Reuters/Ipsos survey taken last week found 60% of the U.S. public views Trump unfavorably, with 34% viewing him favorably.

Talk of election fraud is unlikely to resonate with the crucial voters who swing between both major parties in elections.

That same poll found that 45% of independent voters view the 2020 election as legitimate, while 24% believe fraud was involved and 31% didn't have an opinion. More than 70% of voters said Trump is at least partly responsible for the Jan. 6 attack on the Capitol.

GOVERNOR GAMBIT

Republicans could also lose the governor's mansion in Arizona, particularly if Lake emerges as the nominee.

Lake, a former TV news anchor, has been a leading proponent of Trump's election-fraud claims in a diversifying state that has been shifting toward Democrats and went for Biden in 2020.

"I know for a fact we will no longer accept rigged elections," she said at the rally with Trump, whom she referred to as "Superman."

Former Vice President Mike Pence recently stumped for Lake's more mainstream opponent, Karrin Taylor Robson, in defiance of Trump.

Alex Conant, a Republican strategist and former top aide to Senator Marco Rubio, said Republicans want the election to be a referendum on Biden and his handling of the economy.

"Candidates that don't come off as qualified or say things that turn off independent voters have a tough time getting across the finish line even in a very favorable environment," Conant said.

In Michigan, all the leading Republican candidates for governor have said the 2020 election was riddled with fraud.

After a tumultuous race to take on Democratic Governor Gretchen Whitmer, once considered among the nation's most vulnerable governors, the Republican primary has come down to a slate of little-known conservatives. One of them, Ryan Kelley, was arrested last month for participating in the Jan. 6 Capitol siege.

This week, a group backed by the Democratic Governors Association began running TV ads in the state attacking Dixon, a conservative media personality and self-styled "working mom of four" who has emerged as the putative favorite.

The ads ostensibly aim to boost more extreme candidates such as Kelley, part of a risky Democratic strategy to elevate Republicans whom Democrats view as easier to beat in November.

(Reporting by James Oliphant; Additional reporting by Moira Warburton; Editing by Colleen Jenkins and Daniel Wallis)