Scott Brown calls GOP's abortion platform 'a mistake'

Sen. Scott Brown (R-Mass.) on Tuesday called Republicans' strict opposition to abortion rights in the party platform "a mistake."

Republicans are set to adopt a platform, ahead of their convention next week, that calls for a constitutional amendment banning abortion. Brown — whose race against liberal favorite Elizabeth WarrenElizabeth Ann WarrenWarren: Trump is a 'racist bully' Poll: Oprah would outperform Warren, Harris against Trump in California Democrats continue to dismiss positive impacts of tax reform MORE could decide which party controls the Senate — said the abortion plank is too rigid.

"Even while I am pro-choice, I respect those who have a different opinion on this very difficult and sensitive issue," Brown said in a letter to Republican National Committee Chairman Reince Priebus. "Our Party platform should make the same concession to those of us who believe in a woman’s right to choose."

Brown's race is all the more vital to Republicans in the wake of Rep. Todd Akin's (R-Mo.) refusal to drop out of the Missouri Senate race.

Although Akin's opponent, Sen. Claire McCaskillClaire Conner McCaskillNSA spying program overcomes key Senate hurdle Senate campaign fundraising reports roll in Dems search for winning playbook MORE (D-Mo.), has been widely seen as the most vulnerable Senate Democrat this cycle, Akin's comments about "legitimate rape" could swing the race in her favor. With Missouri potentially out of reach, Brown's race could become even more crucial to the GOP's chances of winning the Senate.

"If we are to grow and succeed in all parts of this great nation, we must be a 'big-tent' party," Brown said in his letter to Priebus. "There are people of goodwill on both sides of the abortion issue, and we need to send a message to voters that there is room in the Republican Party for differing perspectives."

Democrats have already sought to attack the entire Republican Party — and Brown in particular — on divisive women's health issues. After the Senate defeated a proposal to repeal the Obama administration's contraception mandate, Sen. Charles SchumerCharles (Chuck) Ellis SchumerDemocrats will need to explain if they shut government down over illegal immigration White House: Trump remarks didn't derail shutdown talks Schumer defends Durbin after GOP senator questions account of Trump meeting MORE (D-N.Y.) singled out Brown as an incumbent who would have a hard time defending his support for the measure.

The GOP's 2012 platform, which is still being drafted, contains essentially the same language on the subject as the party's platforms in 2000, 2004 and 2008. It calls for a constitutional amendment restricting abortion and is silent on whether there should be exceptions in cases of rape and incest.

Although presidential candidate Mitt Romney supports such exceptions, the Akin controversy has given Democrats a new opportunity to highlight the fact that his running mate, Rep. Paul RyanPaul Davis RyanGOP leaders pitch children's health funding in plan to avert shutdown Lawmakers see shutdown’s odds rising Fix what we’ve got and make Medicare right this year MORE (R-Wis.), opposes abortion rights even in cases of rape.

Brown said he would campaign on his own platform, not the broader GOP agenda.

"But the Republican Party would be well-served to recognize in its platform that you can be pro-choice and still be a good Republican," he said. "I hope you and the Platform Committee will recognize this reality as you finalize this year’s Platform document."