The neck-and-neck contest is one of several that could be the Senate majority-maker by determining whether Democrats hold on to the chamber with a razor-thin margin.

Nonpartisan election forecaster Cook Political Report shifted the race on Monday from “leans Democrat” into the “toss-up” column, joining the likes of Michigan, Ohio, and Wisconsin.

In separate polls released this week, McCormick led Casey for what appeared to be the first time in the race.

A survey from Atlas Intel showed Casey trailing McCormick 47.1% to 48.3% but within the margin of error of plus or minus 2.2 percentage points. In September, the same firm had Casey up by roughly 2 points in the Keystone State.

Casey outperformed the top of his ticket in the crucial swing state, with Vice President Kamala Harris trailing former President Donald Trump 46.5% to 49.8%.

Another poll, from GOP pollster Trafalgar Group, had McCormick up 47.2% to 46.8% with a margin of error of plus or minus 2.9 percentage points.

Casey’s overall polling average leads McCormick by less than 2 points.

“It’s time for a change, and as a 7th-generation Pennsylvanian, combat veteran, and PA job creator, Dave McCormick will bring new leadership and fresh ideas to the Senate when Pennsylvania elects him on November 5,” McCormick spokeswoman Elizabeth Gregory told the Washington Examiner in a statement.

McCormick is the former CEO of hedge fund Bridgewater Associates.

Casey is seeking a fourth consecutive term. His campaign did not respond to a request for comment, but it has sent fresh fundraising pitches to supporters based on the recent polling and ratings shift.

One said McCormick “has a real chance of winning and flipping Pennsylvania red.” Another said he’s “running out of time to pull back ahead and win” with early voting already underway.

“If Bob loses, Democrats will lose the Senate,” another said.

In the final two weeks before Election Day, Democrats have more than $18 million in ads reserved for Casey compared to about $29 million for McCormick, according to the ad-tracking firm AdImpact.

Senate Republicans’ campaign arm accused Casey of now “desperately attempting to tie himself to Donald Trump” with an ad last week creating distance with President Joe Biden and embracing Trump on trade policy.

“We knew this race was a toss-up when Bob Casey started running ads claiming he was President Trump’s best friend even though he voted to impeach him twice,” National Republican Senatorial Committee spokesman Philip Letsou said. “Bob Casey is desperately trying to throw Kamala Harris under the bus to save his own political career — it won’t work.”