Even if the House takes days, there's a strong shot you'll know who controls the Senate before midnight.

Why it matters: Ohio and Montana will decide Chuck Schumer's fate, and both states are fast at counting votes.

• Ohio closes at 7:30pm ET.
• Montana closes at 10pm ET.
• The blue wall states with toss-up Senate races — Pennsylvania, Wisconsin and Michigan — might not have definitive results until tomorrow.

Zoom in: Tonight on Axios.com, we're keeping the same obsessive focus we've had for months with a congressional balance of power tracker.

• Mitch McConnell's Senate Republicans can take the majority by flipping any of the states above, plus Nevada or Arizona.
• Schumer's Democrats can add a buffer if surprisingly embattled GOP incumbents fall in deep-red Nebraska and Texas, or Sen. Rick Scott loses in Florida.

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Ad spending for Senate races this cycle blew past $2.5 billion, according to data from AdImpact.

Why it matters: Senate Democrats face a tough task to keep their majority. But if they lose it, it won't be because of their lack of resources.

• That includes more than $526 million in Ohio ad spending alone.
• Pennsylvania racked up $351 million.
• Montana had over $276 million spent on ads in its Senate race. There are fewer than 1 million registered voters in the state.

The bottom line: Overall, Democratic campaigns, organizations and PACs will outspend Republicans by over $200 million in the Senate races.

— Stephen Neukam

Today's arrest of a man accused of attempting to bring a flare gun, lighter and "accelerant" into the U.S. Capitol is reigniting simmering concerns among lawmakers about security around the 2024 election.

• Why it matters: The arrest is "not a good omen for the next couple of months," a senior House Democrat told us, saying it's created anxiety among staff.

Capitol police chief Thomas Manger told reporters the suspect, identified only as a white male from outside D.C., was arrested at a security checkpoint at the Capitol Visitor Center at roughly 12:20 pm ET.

• Manger said the man "had papers with him that he said was his intent to deliver ... to Congress" and that officers were still interviewing him and reviewing his social media as of this afternoon.
• The Capitol Police are "on heightened alert" around the election and "have an enhanced posture in terms of our security currently," Manger told reporters.
• That will continue "through November, through December, through January, all the way through the inauguration," Manger added.

— Andrew Solender