The Democratic Majority for Israel, a centrist group concerned about progressive Democrats increasingly vocal criticism of the Israeli government, is mounting a last-ditch effort to thwart Sen. Bernie Sanders (I-Vt.) ahead of the Iowa caucuses.

But rather than focus on Sanders interest in boundary-pushing policies like leveraging U.S. aid to change the Israeli governments behavior or his embrace of pro-Palestinian surrogates, the group targeted the issue of his electability in a general-election matchup with President Donald Trump .

Its new 30-second ad features primary voters expressing concern about how Sanders socialism and his recent heart attack will land in battleground states a focus that reflects mainstream Democrats long-standing fears about his candidacy.

For all of the evidence that Sanders has crossover appeal with some independents and even Republicans , his campaign has done little to make the case for his electability in any conventional sense of the term.

Sanders has not always shied away from the argument. In September, he conducted a Bernie Beats Trump tour through six Iowa counties that had flipped from supporting President Barack Obama to voting for Trump. It was an explicit bid to persuade the party that he is uniquely capable of bringing the mostly white, working-class voters who have abandoned Democrats back into the fold.

But compared to his rivals, who are making their ability to beat a Trump a key part of their closing argument to Iowans, Sanders has been relatively quiet.

The Sanders television ads that have been airing in Iowa for the past month tout, among other themes, his reliance on grassroots donors, his championship of Medicare for All, and his support for abortion rights and pay equity, according to the media monitoring firm Advertising Analytics. But none expressly addresses Sanders electability against Trump.