You forgot to mention the tens of millions the NRA spends on opposition ads....
"....The NRA and its allies in the firearms industries, along with the even more militant Gun Owners of America, have together
poured nearly $81 million into House, Senate, and presidential races since the 2000 election cycle, according to federal disclosures and a Center for Responsive Politics analysis done for the Center for Public Integrity.
The bulk of the cash—
more than $46 million—has come in the form of independent expenditures made since court decisions in 2010 (especially the Supreme Court’s Citizens United decision) essentially redefined electoral politics. Those decisions allowed individuals, corporations, associations, and unions to make unlimited “independent” expenditures aimed at electing or defeating candidates in federal elections, so long as the expenditures were not “coordinated” with a candidate’s actual campaign.
“Members of Congress pay attention to these numbers, and they know that in the
last election cycle the NRA spent $18.6 million on various campaigns,” says Lee Drutman, who has studied the role of gun money in politics for the Sunlight Foundation. “
They know what the NRA is capable of doing and the kinds of ads they’re capable of running, and especially if you’re someone facing a close election,
you don’t want hundreds of thousands and potentially millions of dollars in advertising to go against you.”....
What the NRA’s Millions Do?and Don’t?Buy – Mother Jones
The NRA may not have contributed as much directly to individual campaigns....but they spent tens of millions in opposition ads against anyone that doesn't vote pro-NRA.