Vice President Biden is scheduled to headline a fundraiser for Alex Sink Wednesday in the hotly contested Florida special election. 

Biden is the latest Democratic reinforcement effort to help boost their candidate against GOP nominee David Jolly for the special election to succeed the late Rep. Bill Young (R-Fla.). 

The vice president's visit comes as Republicans are doubling down on Sink, and the Chamber of Commerce has launched their second ad against the Democrat. 

The Chamber’s new ad charges that Sink supports ObamaCare, which it describes as a “disaster for families and seniors” and has resulted in “canceled health plans, higher premiums, Medicare cuts, people losing their doctors.”

“With Alex Sink, the priority is ObamaCare, not us,” the narrator says in the ad.

The ad is the second running as part of a high six-figure buy made by the Chamber in the district. The group’s first ad featured former Florida Gov. Jeb Bush endorsing Jolly. 

Multiple polls, both public and private, have shown a tight race for Young’s seat, with Sink slightly leading Jolly or within the margin of error — a development that’s surprised some Republicans, who felt they faced an uphill battle with Jolly as their nominee

Republican outside groups have invested more than $2 million in the race so far, and Democratic groups are also spending millions to hammer Jolly, largely focusing on his lobbying background as a major weakness for his candidacy.

Republicans believe that, even with a flawed candidate like Jolly, who’s weighed down by his lobbying background, the political atmosphere in the district — and particularly opposition to ObamaCare — favors them.

But Democrats have signaled they're willing to put up a fierce fight for what became for them a top pickup opportunity with Young's passing. Biden's stop in the state will help pad Sink's already considerable fundraising advantage and help her combat attacks from moneyed Republican groups.