RICHMOND — A bunch of Virginia legislators, mostly Republicans, stood behind Gov. Ralph Northam (D) as he rolled out a highway-improvement bill on the eve of the General Assembly’s Wednesday kickoff.

“I just want to let you know this is the way it works here in Virginia,” Northam joked to a newcomer, Del. Ronnie Campbell (R-Rockbridge), who won a special election in December. “Every idea that I have gets bipartisan support.”

Not quite.

Northam has faced GOP pushback on other legislation he is pitching in the 46-day session. Tuesday’s gathering on Capitol Square suggests there may still be room for compromise, despite the fact that all 140 seats in the state House and Senate will be on the ballot in November — a dynamic that will color the entire session.

Sen. Mark D. Obenshain (R-Rockingham), a fiscal conservative, was among those backing legislation to create the I-81 Corridor Improvement Fund — even though the bill calls for $2.2 billion in fixes to be paid for with new tolls.

“Believe me, it’s an uncomfortable position to take, to say that I would be supportive of tolls, but under the right circumstances, I am,” Obenshain said, recalling his own “close encounter with the front end of a Peterbilt” on the highway that stretches 325 miles in central and southwest Virginia.

The legislative session begins as Northam, a former lieutenant governor and state senator, enters his second year in the Executive Mansion. He won the office in November 2017 amid a blue wave fueled by suburban antipathy toward President Trump. The same wave nearly wiped out the GOP’s 2-to-1 majority in the House. Fifteen new Democrats and some GOP defectors enabled Northam to expand Medicaid under the Affordable Care Act in his first year, an enormous win that had eluded predecessor Terry McAuliffe (D) for four years.

Whether Northam can pull off another big victory this year is unclear.

But Democrats have a clear agenda — gun control, no-excuse absentee voting, tax relief for­ ­lower-income Virginians — that they may be able to leverage at the polls if Republicans defeat it during the session, according to University of Mary Washington political scientist Stephen Farnsworth.

“Very effective D effort to set the stage for the 2019 elections in #Virginia,” Farnsworth tweeted. “Republicans may block much of this agenda, but if so Democrats will use these measures to frame the commonwealth’s midterm elections.”

Republicans, who have not won a statewide election since 2009, enter the session desperate to find their footing in once-friendly suburbs. The president’s unpopularity, which helped Democrats flip three suburban congressional seats in November, put Republicans at risk of losing the state House and Senate. The GOP has a mere two-seat majority in both chambers.

Del. David LaRock (R-Loudoun), one of the few Republicans in the Northern Virginia delegation, tried to capture the peril in a fundraising appeal issued Tuesday afternoon, comparing himself to a polar bear clinging to a melting iceberg.

“Save Endangered Delegate Dave from Extinction!” began the missive, which went on to describe the delegate as a “High-value target of liberal extremists” who is “Not cute,” “Not fuzzy,” “But crucial to keep around.”

At stake in the elections is control of not just the legislature, but also the redistricting process that will determine the contours of Virginia’s congressional and state legislative maps for the next decade.

As it is, the map for this year’s elections is unsettled. A federal-district court found that 11 districts in Hampton Roads and greater Richmond were racially gerrymandered and has appointed a “special master” to draw new boundaries that will also affect adjacent districts. The U.S. Supreme Court has agreed to hear an appeal filed by Republican legislators defending the existing map, but on Tuesday, the high court rejected their request to halt the special master’s mapmaking in the meantime.

House Speaker Kirk Cox (R-Colonial Heights) has encouraged Republicans to focus on “practical” problems. In the Senate, a group of Republicans has proposed a package of bills intended to lower the cost of health insurance.

Some Republicans are choosing to champion causes that their party has not ordinarily embraced, such as working to make Virginia the 38th state to ratify the Equal Rights Amendment. Some strategists predict softening on certain social issues, such as gay rights.

At a recent GOP retreat, Cox said the party was working to field a more diverse slate of candidates. D.J. Jordan, an African American who once chaired the state’s Board of Social Services, announced this week that he would run as a Republican for the House seat that Del. Liz Guzman (D-Prince William) flipped last year.

Just ahead of the session, two of the party’s more polarizing figures announced that they were stepping away from politics.

Corey A. Stewart, who made the preservation of Confederate statues a rallying cry in his failed bid for U.S. Senate last year and for the gubernatorial nomination in 2017, said this week that he is leaving politics “for the foreseeable future.”

Sen. Richard H. Black (R-Loudoun), a vocal social conservative who drew international notice for twice meeting with Syrian President Bashar al-Assad, is retiring. Loudoun County Supervisor Ron A. Meyer (R) jumped into the race this week with a promise to focus on transportation.

Perhaps the most pressing issue in Richmond this year concerns how to respond to the federal tax overhaul championed by Trump and passed by congressional Republicans.

The 2017 federal law limited deductions on mortgage interest and property taxes and doubled the standard deduction to make up for those changes, probably making the standard deduction more appealing. Under current law, Virginians who take the standard deduction on their federal returns must do the same on their state tax returns, which would lead to higher state tax bills because Virginia’s standard deduction remains unchanged.

If Virginia leaves its tax code untouched, an extra $1.2 billion is expected to pour into the state’s coffers every two-year budget cycle until the federal cuts partially expire in 2024. Northam wants to use half of that money to fund tax breaks for households making less than $54,000 a year and put the rest toward “historic” investments in the state’s reserve fund, schools and other government programs.

House Republicans regard that approach as a tax hike that prevents Virginians from reaping the full benefits of the federal cuts. They have offered a plan to allow taxpayers to itemize on their state taxes regardless of what they do on their federal returns. It also would increase the state standard deduction from $3,000 to $4,000 for individuals and from $6,000 to $8,000 for married couples.

The disagreement is likely to complicate efforts to make the usual midpoint amendments to the state’s $117 billion two-year spending plan, which was approved in May and took effect July 1.