Updated Tuesday with audio from the "St. Louis on the Air" veto session preview.

The Missouri General Assembly’s veto session, which begins Wednesday, generally shuffles into the background during an election year. While legislators could have very busy day (or two), the unrest in Ferguson has sucked up most of the state’s political oxygen this year.

To be sure, none of the issues that could be debated this week have a direct connection to Ferguson. But Gov. Jay Nixon spent time that he would have used to defend his vetoes dealing with the aftermath of Michael Brown’s death. He also encountered plenty of criticism from some Democrats, including lawmakers who may be needed to prevent veto overrides.

All these things could affect what happens this week. Even though some professional political aggregators may not approve, here are five things to watch out for when the veto session is gaveled into session.

What will be the main event?

In the past two veto sessions, it was easy to pick out the most high-profile override battles. The 2013 veto session focused on tax cuts and gun nullification while the 2012 session centered primarily on a bill taking aim at a federal contraception mandate.

Jason Rosenbaum, St. Louis Public Radio

This time, none of the bills sticks out as the “main event.” One reason could be that lawmakers already overrode Nixon’s veto of a tax cut bill earlier this year. The other potentially big ticket item — a bill overhauling the state’s school transfer law — isn’t likely to have enough votes.

So what are the prime candidates? A batch of bills enacting various tax breaks, which Nixon derisively labeled the “Friday favors”; legislation enacting a 72-hour waiting period for abortions; and a bill defining captive deer as livestock.

One wildcard could be a showdown over Nixon’s line item budget vetoes. There’s disagreement about whether the legislature can override them en masse or whether they’ll have to handle them individually. If it's the latter, lawmakers may spend most of their time trudging through that process.

Can Republicans have another record-breaking session?

Even though the legislature didn’t have enough votes to override the tax cut or gun nullification bills last year, they still managed to enact 10 bills over Nixon’s objections. House Speaker Tim Jones, R-Eureka, already predicted “at first blush that this session may very well be as historic as the last one."

Indeed, many of the bills that Nixon vetoed passed by overwhelming margins — including some of the so-called “Friday favors” bills. There’s no guarantee lawmakers who voted for those bills will stick with their original votes, but lawmakers may exceed their tally from last year.

Of course, the success or failure of a veto session may hinge on whether the bigger-ticket items get overruled as opposed to sheer quantity.

Will conservative Republicans in the Missouri Senate be kingmakers?

Last year, Missouri Republicans had absolutely no room for error to override bills. That was because they had 109 members at the time — the exact number needed to overrule Nixon’s objections.

Jason Rosenbaum, St. Louis Public Radio

Thanks to two special elections earlier last month, House Republicans will have 110 members at the start of veto session — providing a little wiggle room on bills that may particularly tight. But the real drama may end up in the Missouri Senate.

That’s because Republican Scott Rupp resigned earlier this year to join the Missouri Public Service Commission. That means Republicans are down to 23 members – the exact number needed to override a veto. The Senate’s more conservative members — such as Sens. John Lamping, R-Ladue, Ed Emery, R-Lamar, and Rob Schaaf, R-St. Joseph — may decide to vote against bills they see as fiscally imprudent.

That would leave the Republicans short of the numbers to override Nixon. Unless…

How will Democrats matter this year?

During a Politically Speaking podcast earlier this year, House Minority Leader Jake Hummel, D-St. Louis, noted how his caucus gains a lot of power during veto session when Democrats can spell the difference between a bill being overridden or thrown into the dustbin.

Jason Rosenbaum, St. Louis Public Radio

Some House Democrats — such as state Senate contenders Jeff Roorda and Ed Schieffer — may break ranks to override Nixon on conservative bills, such as bills requiring a 72-hour waiting period for abortion and relaxing firearms regulations. There may also be support for certain tax break bills that Democrats deem acceptable.

Democrats may play a more important role in the Senate, especially if the some Republicans decide to sustain Nixon’s vetoes. Plenty of Senate Democrats broke ranks during the last veto session, but Republicans also had 24 members – which may have changed the calculus for how those senators voted.

Will Senate Democrats decide to filibuster anything? That hasn’t happened in the last two veto sessions, but it could have affect which bills come up for an override attempt.

What impact did Ferguson have on Nixon’s ability to sustain his vetoes?

Throughout his tenure as governor, Nixon has been particularly adept at pointing out what he perceives as flaws in bills. He often showcases these snafus in a very public way – as evidenced by how he barnstormed the state to upend last year’s tax cut.

Bill Greenblatt | UPI

Nixon was going through a similar exercise earlier this year to combat the “Friday favors.” But after the crisis in Ferguson reached a fever pitch, he had to devote his attention to keeping protests under control – not lambasting the work of the Republican legislature. Short-circuiting that process could matter this week, especially if Nixon couldn’t use his bully pulpit to convince a few Republican legislators to sustain his vetoes.

Nixon also faced some very public criticism from some Democrats during the Ferguson unrest – particularly from state Sens. Maria Chappelle-Nadal, D-University City, and Jamilah Nasheed, D-St. Louis. It will be worth watching to see if some members of the state’s legislative black caucus abandon Nixon on certain veto overrides.

This isn’t necessarily a sure thing. After all, the school transfer legislation showcased a particularly public divide between African-Americans in the House and Senate. But this week could indicate whether Nixon’s already tenuous ability to influence a hostile legislature is fractured further.

On the Trail, a weekly column, weaves together some of the intriguing threads from the world of Missouri politics.