Gina Brewer, the manager of Texas Gun, behind the counter in her San Antonio store. (Photo by Gilles Mingasson/Getty Images)

Maybe Monday’s Senate gridlock on guns would have happened anyway, but it probably didn’t hurt the gun lobby’s cause that the National Rifle Association already has spent close to $2 million trying to help incumbent Republicans hold their majority in Congress’ upper chamber.

And the NRA has only begun to fight: The group’s latest campaign finance report, filed Monday with the FEC, shows that it ended the month of June with more than $14.7 million to spend in the general election.

While the 9/11 attacks famously inspired a brief interlude of solidarity on Capitol Hill, the same cannot be said for the most deadly act of terror on American soil since then — the gunning down of 49 people and wounding of more than 50 others at an Orlando nightclub. The Republican-controlled Senate consented to vote on proposed gun-control measures only after a 15-hour filibuster by Sen. Chris Murphy (D-CT), whose state lost 20 schoolchildren in a 2012 shooting spree. The maker of the gun used in the Newtown massacre on Monday asked a judge to throw out a lawsuit brought by families of the victims.

All four measures that the Senate voted on — two offered by Republicans and two offered by Democrats — failed on procedural votes, which required the support of a supermajority of 60 senators. Only one member of the Senate voted consistently against his party on all four votes: Sen. Mark Kirk, an Illinois Republican who is up for reelection in a race that’s widely regarded as one of the nation’s most competitive this year, supported the two Democratic amendments and voted against those offered by his Republican colleagues Chuck Grassley of Iowa and John Cornyn of Texas.

See how senators voted on the gun measures.

Two other endangered Republican senators, Pat Toomey of Pennsylvania and Kelly Ayotte of New Hampshire, complained that leaders of both parties were gaming the votes for election purposes, rather than making an honest attempt to reach a compromise. “We shouldn’t be just talking past each other and voting on things we know are going to fail,” said Toomey, who two years ago offered a bipartisan bill to strengthen background checks for gun purchasers that also failed on a procedural vote. Ayotte is calling for a Senate vote on a compromise measure authored by Sen. Susan Collins (R-ME).

The NRA, which sent out an alert to members asking them to call members of Congress to stop the Democratic measures, is already making its presence felt in competitive Senate races. Based on an analysis of Federal Election Commission data tabulated by the Center for Responsive Politics along with an independent examination of more recently arrived reports at the FEC, BillMoyers.com calculates that the NRA has already spent $1.97 million trying to influence Senate races.

That includes a $75,000 check to the National Republican Senatorial Committee, the party organization charged with maintaining the GOP’s Senate majority, and contributions to individual states and campaigns. Of the 22 Republican senators seeking reelection this year (a number that could jump to 23 if Sen. Marco Rubio of Florida changes his mind later this week about retiring), the NRA, through its various committees, has already provided some form of financial assistance to 18, according to data compiled from CRP and the FEC. The NRA has also donated to some Republican challengers in Senate races but for the purposes of this analysis, we focused on only senators who cast votes on Monday and on contributions to their current campaigns. PBS has compiled lifetime NRA donations for all of the senators who opposed tougher gun control.

See the full list of Republican senators receiving NRA contributions for this year’s elections.

By far the biggest beneficiary of NRA funding so far: Sen. Rob Portman, an Ohio Republican who faces a tough reelection fight in a swing state this fall. Between the “independent expenditures” — donations that, because they are purportedly not “coordinated” with a campaign, can be made in unlimited amounts — the NRA made supporting Portman and opposing his Democratic opponent, former Ohio Gov. Ted Strickland, the gun lobby has spent more than $700,000 on the Ohio race. The NRA can help candidates in several ways: through its political action committee’s donations to candidates (up to a limit of $5,000 per election or $10,000 for the primary and general campaign), through donations to state political committees (limited to $5,000 per year) and through so-called “independent expenditures” by both its political action committee and a separate committee called the NRA Institute for Legislative Action.

However formidable, the NRA’s bottom line is only one measure, and perhaps not the most important one, of the organization’s power. More telling is a number beneath the big number: Of the more than $700,000 in donations the NRA has raised this year, some 87 percent are “unitemized” — meaning they are donations of $200 or less. The fact that the NRA is collecting that much money in small bills gives some measure of the grass-roots support it can mobilize to call, email and otherwise give politicians advice on how to vote — and then to go to the polls and retaliate against or thank their elected representatives.

In 1994, when Democrats lost their majority in the House for the first time in a half century, the vote for the assault weapons ban was one of several factors that cost the party, at least in the eyes of then-President Bill Clinton. In his autobiography, My Life, Clinton recounts how a number of Democrats, including Jack Brooks of Texas, a 40-year House veteran and, Clinton wrote, “one of my favorite congressmen,” warned him that passage of the assault-weapons ban would bring the wrath of gun owners down on Democrats. Clinton was convinced common-sense arguments would overcome the gun lobby. But results at the ballot box proved that the alarmed Democratic lawmakers “were right and I was wrong,” Clinton wrote. “The price of a safer America would be heavy casualties among its members.” One of them was Brooks.

When the assault-weapons ban came up for renewal in 2004, Congress let it expire without a vote.