As the two major parties prepare for an epic battle for control of the Senate this year, some Democrats are questioning the decision by one of their richest political action committees to sit out the campaign and hold its money for Hillary Clinton’s expected campaign for the White House in 2016.

Some Democrats argue that the decision could help the Republicans seize control of the Senate next fall, making it impossible for President Barack Obama to get anything done and perhaps setting the stage to do the same for Clinton even if she wins the presidency. Others counter that the committee always was devoted to presidential campaigns – first for Obama and now for Clinton – and that congressional Democrats will still have plenty of money this year for hard-fought campaigns.

At the center is Priorities USA Action, once Obama’s big campaign fundraising group. Since it helped him win re-election in 2012, the political action committee has morphed into an important fundraising vehicle for Clinton’s potential campaign and is devoting its dollars and energy to promoting her.

The group raised $79.6 million for the 2012 campaign. Taking it out of the action “removes the top echelon,” said Sheila Krumholz, the executive director of the nonpartisan Center for Responsive Politics.