(CNN) - The Tea Party Express is predicting large crowds for its five events Thursday and Friday aimed at unseating Rep. Bart Stupak of Michigan. The five events are being held in the Democratic congressman's large and rural district, which includes the entire upper peninsula of Michigan.
The rallies come as sources tell CNN that the top two House Democrats called Stupak to urge him to stay in Congress. A Stupak spokeswoman didn't confirm nor deny rumors that Stupak is considering retiring from Congress.
"Every two years, Congressman Stupak discusses with his family and his constituents whether to seek reelection. He believes that is what the people of the First District of Michigan deserve," said Stupak spokeswoman Michelle Begnoche.
Begnoche does tell CNN that Stupak's campaign plans are underway, and has already gathered the 1,000 signatures needed to formally file for re-election by Michigan's deadline, May 11th.
Three Democratic sources tell CNN that House Speaker Nancy Pelosi and House Majority Leader Steny Hoyer have both called Stupak to urge him to stay in Congress.
One of the sources says that the top two House Democrats told Stupak that he's a valued and important member of the caucus, that there's still a lot more work to be done that will benefit Michigan and that the caucus will be there for him.
Despite the rumors and cryptic statement from Stupak's office, several Michigan Democrats who know Stupak tell CNN they do not think he will retire.
The socially conservative, anti-abortion rights Democrat gained national attention last month by helping deliver the remaining votes House Democrats needed to pass health care reform. Stupak cut a deal with the White House that he says ensures no taxpayer money will be used to fund abortions. The bill was signed into law last month by President Obama.
The Tea Party Express says it is targeting Stupak because of his health care vote. The group began what they call a $250,000 television and radio campaign against the nine term congressman. Tea Party Express organizers say that local coordinators are predicting crowds of what they describe as "historic proportions." But cold weather and snow in the area could keep the crowd size down.
"People are angry, they feel that Congressman Stupak betrayed them and they are determined to hold him accountable," says Tea Party Express Chairman Mark Williams.
Stupak is also now facing criticism from abortion rights groups who think he forced too many abortion restrictions into the health care bill. They are trying to raise money for his Democratic primary challenger, Connie Saltonstall.
Still, several Michigan political experts tell CNN they believe it would be hard to unseat Stupak. He is a popular figure in his district, and the anti-abortion, anti-gun Democrat still seems to fit the largely Catholic, socially conservative constituency.
And, so far, Stupak's potential challengers are unknown and not well funded.
"The idea that Stupak, who has been a congressman for 18 years can be beaten by somebody with no money – from left or right – with no constituency, is unlikely," said Bill Ballenger of Inside Politics Michigan, a political newsletter.
The five rallies are part of the Tea Party Express's third national bus tour, which is scheduled to end on April 15. The Tax Day event is expected to draw various tea party and conservative groups to the nation's capital.
The tour, with a slogan of "just vote them out," is highlighting the states and districts of lawmakers that Tea Party Express is working to defeat in this year's congressional elections.
The tour kicked off in Searchlight, Nevada, which is the hometown of Senate Majority Leader Harry Reid. Tea Party Express organizers say that Reid and Stupak are their top two targets.
–CNN producer Evan Glass contributed to this report