WASHINGTON (AP) — Senate Majority Leader Mitch McConnell thinks it's dangerous for his party to challenge President-elect Joe Biden's election triumph. But some Republicans are charging ahead anyway, and this time McConnell is facing dynamics he can't fully control.

Despite the Kentucky Republican's opposition, 13 GOP senators have said they will join scores of their House colleagues Wednesday and object when Congress formally affirms Biden's Electoral College victory. The effort, certain to fail, has been spurred by the soundly defeated President Donald Trump as an unjustified, last-gasp effort to override the election results, which all 50 states have already certified.

McConnell has warned his colleagues that the showdown is risky because it will force GOP senators, including those in potentially tough 2022 reelections, to decide whether to support or oppose the tweet-happy Trump in a fight they are sure to lose. In mid-December, McConnell privately warned them that pressing the issue would force a "terrible vote," even as he publicly congratulated the Democrat Biden for his win, ignoring Trump's refusal to concede.

To drive home his views, GOP aides say McConnell plans to be first speaker when the initial objection is raised during Wednesday's joint session of Congress and senators return to their chamber for a two-hour debate and vote. McConnell has also made clear the Senate will meet all night if necessary to handle all the objections, the aides said.

McConnell has actively avoided confrontation with Trump whenever possible, but he is plainly fed up with the Trump chaos. His remarks Wednesday are sure to leave no doubt how seriously he views the vote, which goes to the heart of the orderly transfer of power in American democracy.

But McConnell can't prevent the objections, which are allowed by the Constitution and federal law if one representative and one senator challenge a state's electoral votes. He's also facing overpowering political dynamics, including some senators' expected 2024 presidential ambitions, others' desire to protect themselves from 2022 primaries prompted by an offended Trump, and the temptation to use the fight to raise money and buttress support from Trump's ardent followers.

"You've got people who'd like to be presidential candidates who are acting in the best interests of being candidates," said David Winston, a political adviser to congressional GOP leaders.

Trump's claims of voter fraud, which he began lodging months before Election Day, have been rejected by Republican and Democratic officials in state after state and numerous judges, including the conservative-dominated Supreme Court. Trump's former attorney general, William Barr, has said there is no evidence of fraud that could change the election outcome.

Freshman Sen. Josh Hawley, R-Mo., has said he will challenge Pennsylvania's electoral votes. Sen. Ted Cruz, R-Texas, leading a group of 11 senators who want to create a commission to examine groundless allegations of election fraud, is expected to challenge Arizona's votes. Both men are expected to run for president in 2024.

Sen. Kelly Loeffler, R-Ga., may also challenge the results in her state. Pennsylvania, Arizona and Georgia were all pivotal states that Biden won on his way to his 306-232 Electoral College win.

Spokesman David Popp said McConnell is not pressuring colleagues to vote with him. But he's made his views clear, last week telling GOP senators that he considers the vote the most consequential of his career and sharing his views with numerous colleagues who've sought him out.

His most powerful allies are with him, with GOP Whip John Thune of South Dakota earning a Twitter threat from Trump after predicting the Senate effort would "go down like a shot dog."

McConnell is trying to steer his colleagues to a conservative argument that Congress shouldn't overrule states' election decisions. He's gained momentum in recent days, winning support from influential members including moderate Sen. Rob Portman, R-Ohio, and conservative Sens. Tom Cotton, R-Ark., and Pat Toomey, R-Pa.

Aides expect a majority of GOP senators to join McConnell and all Democrats in shooting down the electoral vote challenges. Cotton is considered another presidential contender.

McConnell, 78, has served as Republican leader since 2007 and is the longest-serving Senate GOP leader in history. But his status as majority leader is in peril for reasons outside the intraparty Electoral College tussle. The GOP majority in the Senate teetered early Wednesday as Democrat Raphael Warnock won one of Georgia's two Senate runoffs; a razor-thin margin separated the Republican and Democratic candidates in the second contest. Losing both would cost McConnell his majority.

McConnell hasn't shied from past battles with the party's conservative base. He's won more than not lately, but in 2010 and 2012 fringe GOP candidates in Nevada, Colorado and Indiana appeared to cost the party seats. But he turned the tide in 2014, beating back a primary challenge of his own and leading the GOP to Senate control after eight years in the minority.

Cruz's group includes all four freshmen Senate Republicans, a troubling sign for McConnell as stalwart allies like Lamar Alexander, R-Tenn., and Pat Roberts, R-Kan., have retired. Each freshman pledged fealty to Trump in their campaigns and are casting the first vote of their Senate careers in line with Trump's wishes.

In an earlier day, freshmen might have been more inclined to side with establishment leadership figures who are likely to be more important than a departing president.