Spending by Trump’s Save America PAC surges amid legal battles over Mar-a-Lago search

By comparison, the National Republican Senatorial Committee -- the GOP fundraising arm charged with flipping the Senate -- started September and the sprint to Election Day with just $16 million remaining in the bank.

Vance, as desperate for his support.

Most candidates would "much rather have somebody come in with a lot of money to drive home your message, rather than a one-day event where you can't control what the main attraction is going to say," said Doug Heye, a veteran Republican strategist and former spokesman for the Republican National Committee.

With control of the Senate on the line, deep-pocketed Republican groups have stepped up to fill the gap, including the Senate Leadership Fund, a super PAC affiliated with Senate Minority Leader Mitch McConnell.

(The McConnell-aligned super PAC announced Tuesday that it was pulling its remaining ad reservations for the month of October out of Arizona, citing increased spending by other Republican groups, including Our American Century.)

New filings with the Federal Election Commission show Las Vegas casino mogul Steve Wynn donated $10 million to Our American Century last month.

That committee has spent nearly $7 million in key states -- including advertising to aid Republican Mehmet Oz's Senate bid in Pennsylvania and to oppose several Democratic senators seeking reelection.