With each passing week, the National Rifle Association wades deeper into this year’s most competitive Senate races.

As of August 26, the gun rights organization had spent at least $2.6 million on four contests considered competitive by the nonpartisan Cook Report. Most of that, as The Trace previously reported, had gone to just one contest: a dog fight in Ohio between Rob Portman, the Republican incumbent, who is battling Ted Strickland, the state’s former governor and a one-time NRA ally.

The roughly $2 million spent in that race, primarily on ads attacking Strickland, was more than all other down-ballot races combined.

Now the group is expanding its reach. According to the latest campaign finance data on independent expenditures, the NRA has, in a substantial manner, come to the aid of two candidates locked in tight races. In Wisconsin, incumbent Republican Ron Johnson has lost ground to a challenger, former Senator Russ Feingold. The Cook Report says that race is now leaning in Feingold’s favor. According to the Federal Election Commission, the NRA reported in September it had spent almost $150,000 in support of Johnson, an outspoken critic of gun control.

In June, after the deadliest mass shooting in American history occurred in Orlando, Florida, amid renewed calls for restrictions on firearms, Johnson said: “We have to quit distracting Americans with these nonsense debates.”

In conservative Indiana, the seat being vacated by Republican Senator Dan Coats is up for grabs. The Cook Report considers this race to be one of six “toss-ups” in the upper chamber. The Republican candidate, Representative Todd Young, is a key NRA ally. In March, in the wake of the death of Justice Antonin Scalia — arguably the country’s most crucial Second Amendment supporter — Young introduced a House measure that read, in part, “the Senate should not confirm a nominee to the United States Supreme Court whose professional record or statements display opposition to the Second Amendment freedoms of law-abiding gun owners.”

The NRA has now spent almost $140,000 supporting Young, who faces Evan Bayh, a former U.S. Senator who earned a D- rating from the NRA in his last election.

For the gun rights organization, the stakes are exceptionally high this cycle. At the federal level, the NRA has essentially become a Republicans-only organization, contributing to the partisan gridlock that has overtaken Congress.

Most Democrats now support new gun restrictions, including measures that seek to close the “terror gap” and expand background checks. If Democrats retake the Senate, the House, and win the presidency, those measures could advance and eventually become law.

Perhaps even more importantly, if Justice Scalia’s seat remains empty for the rest of President Obama’s term, it will be up to the next iteration of the Senate to approve or block the next president’s nominee. The NRA has warned that if Clinton is elected, she will appoint a justice (or justices) who will roll back the landmark District of Columbia v. Heller decision that affirmed for the first time the right of private gun ownership.

As the NRA’s top lobbyist, Chris Cox, likes to remind the group’s membership, in November “the Second Amendment is on the ballot.”

[Photo: Bill Clark/CQ Roll Call]