(CNN)Mitch McConnell isn't backing down in his standoff with Donald Trump.

       On Monday, the Senate Leadership Fund, the super PAC aligned with McConnell, announced that it had booked more than $7 miIlion worth of ad time in Alaska as GOP Sen. Lisa Murkowski tries to fend off a challenge from Kelly Tshibaka, who has been endorsed by the former President. (The group also reserved ad time in six Senate battleground states.)

       The move to defend Murkowski isn't terribly surprising -- McConnell has made clear all along that he supports Republican incumbents, including Murkowski.

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       But the super PAC's decision to commit $7 million -- by way of context, that's roughly how much Murkowski spent on her 2016 reelection race -- to Alaska means that McConnell is sending a not-so-subtle message to Trump: Time to put up or shut up.

       See, Murkowski is crushing Tshibaka in fundraising. As of March 31, Murkowski had more than $5.2 million in the bank to spend on the race; Tshibaka had less than $1 million.

       The incumbent was already on pace to heavily outspend the challenger. And now, with the McConnell super PAC weighing in, the advantage on the pro-Murkowski side is, well, massive.

       Who could help close that sort of financial gap? How about the former President? His Save America PAC had $110 million -- not a typo -- in the bank as of the end of February.

       Except Trump doesn't seem inclined to spend that money. As The New York Times wrote over the weekend in a terrific piece on the Trump political organization:

       "Mr. Trump can be downright stingy. Though he holds rallies for some candidates, for many his support goes no further than an email and a $5,000 check. Mr. Trump has almost never deployed his huge list of supporters to help other politicians raise money."

       Might that stinginess be changing? Trump's PAC did recently give $500,000 to a super PAC attacking Georgia Gov. Brian Kemp. So, maybe?

       What we do know is that McConnell isn't screwing around in Alaska. And the ball is very much in Trump's court.

       The Point : Money alone won't win Murkowski her pitched fight. But it sure as heck will help.