In a closely divided Congress, the Senate’s Mischief Makers could thwart their leaders' best-laid plans with their own agendas.

Why it matters: On Wednesday night, we shared a list of House members who our leadership sources on the Hill consider some of the top troublemakers. But their Senate counterparts may be even more impactful in a 50-50 chamber, where Vice President Kamala Harris holds the tiebreaking vote.

Not all are created equal. Democrats often contend with an outspoken, very progressive wing of their caucus and try to keep centrists from crossing party lines. Republicans have senators who led efforts to invalidate the 2020 election results and flirted with the same conspiracy theories that fueled groups involved in the Capitol siege.

Republicans:

• Rand Paul (Kentucky): The libertarian frequently bucks leadership and stalls compromises. He's not afraid to be on an island within his party.
• Ted Cruz (Texas) and Josh Hawley (Missouri): Both have an eye on the 2024 presidential race, and both will break with leadership for political benefit. The two ignited the Senate debate over challenging the Electoral College votes.
• Ron Johnson (Wisconsin): He didn't hesitate to open political investigations into then-President Trump's opponents, even when Sen. Mitch McConnell advised against them.

Time will tell about whether GOP freshmen Sens. Roger Marshall (Kansas) and Tommy Tuberville (Alabama) also will haunt McConnell's plans, our congressional sources say.

Democrats/Independents:

• Kyrsten Sinema (Arizona) and Joe Manchin (West Virginia) aren't afraid to stray across party lines. The latest example: They had private conversations with Republicans, including McConnell, signaling they wouldn't back Democratic efforts to eliminate the filibuster.
• Bernie Sanders (Vermont): The independent who caucuses with the Democrats is fearless and refuses to fall in line. He and Hawley made an unlikely pair when they teamed up to push leadership for $2,000 stimulus checks in the last COVID relief bill.