In part, that's because they have practically nowhere to go but up. Republicans control two-thirds of the nation's legislative chambers, many by supermajorities.
"Democrats have lost more than 900 seats since President Obama took office, giving the party a lot of room to grow at the state level," said Steven Rogers, a political scientist at St. Louis University.
In a presidential year, Democratic turnout should be higher overall, lifting the party's chances at the legislative level, especially in an era when ticket-splitting has become less common. The "unconventional nature" of the Trump campaign and its relative lack of organization should also help Democrats, said Robert Hogan, a Louisiana State University political scientist.
Nevertheless, the picture at the legislative level is complicated, he said, by Trump's appeal to less-educated, blue-collar white voters who may have traditionally voted Democratic.
Trump's campaign has devoted far less attention and resources to field work and data analytics than typical presidential campaigns. In some places, it doesn't appear to have coordinated its efforts closely with state parties on the ground.
By contrast, Obama has endorsed more than 100 Democrats seeking legislative office, recording robocalls for some of them -- an unprecedented effort from a president in recent years.
"Between this and the likely superior Democratic turnout machine this cycle, the question is how many seats will Democrats take back," said Rogers, the St. Louis University professor.
Democrats have been confident all year about regaining ground they'd lost, particularly in 2014. Two years ago, the GOP took over 11 chambers, many of them in typically blue states.
"We expect to evict Republican majorities from several of the chambers they’ve essentially been 'renting' since the 2014 GOP wave, like those in New Mexico, Nevada, Minnesota, New Hampshire, Maine and Washington, for example," said Carolyn Fiddler, communications director for the Democratic Legislative Campaign Committee.
Fiddler said that "Donald Trump's toxic candidacy" has put more difficult-to-reach chambers in play as well, including the Arizona Senate. Trump's pre-election numbers in Arizona remain lower than those rung up by recent GOP presidential nominees.
Still, with reluctant Republican voters appearing to return to their party in recent polling, taking over chambers such as the Michigan House will be more of a stretch for Democrats.
"The GOP has been favored all cycle to maintain control, even though all of the major tossup seats are in Republican hands," said Susan Demas, editor of Inside Michigan Politics. "At this point, the only thing that could save Democrats is a wave, as many of their targeted races have faded from the map."
Republican officials express confidence that they'll be able to hold onto chambers where the party has a narrow majority, including the state senates in Nevada, New York and West Virginia.
On offense, an expected strong showing from Trump in Kentucky could help the GOP take over the state House -- perhaps unseating Speaker Greg Stumbo himself in the process.
"In Kentucky, Republicans are closer than they’ve been in 100 years to winning the majority back from Democrats in the last chamber in the South under their control," said Ellie Hockenbury, communications director for the Republican State Leadership Committee. "We have several paths to the majority with GOP candidates running in 25 Democrat-held districts carried by Gov. [Matt] Bevin last year."
Republicans have their eye on another elusive target, the Iowa Senate, which Democrats have held with a 26-24 majority since 2010. Polls at the presidential level show Trump carrying Iowa.
"Republicans have a very good chance of flipping the two seats needed to take control of the Senate and complete the trifecta in Iowa, with both legislative chamber majorities and the governor and lieutenant governor seats," said Hockenbury.
Even in states where Hillary Clinton is favored, the legislative map may be scrambled by Trump's candidacy. He may be unpopular in cities and affluent suburbs, but his appeal to white working class voters has put some more rural and traditionally Democratic areas in play, such as the northeastern Iron Range in Minnesota. When Republicans took over the Minnesota House two years ago, nearly all their gains were outside the metropolitan Twin Cities area.
Conversely, Trump's poll ratings among Hispanics remain terrible, and they'll grow as a share of the electorate this year. Early voting suggests Hispanics will turn out in increased numbers, including in some key legislative battlegrounds.
In states such as Colorado and Nevada, where Democrats only have to net a few seats to win chambers, their task shouldn't be too daunting, predicts Jaclyn Kettler, a political scientist at Boise State University.
Given the uncertainty at the top of the ticket, the parties may end up regretting their failure to recruit candidates in many districts that are usually not competitive. More than 40 percent of the nearly 6,000 seats up for grab won't be contested by one of the major parties.
"There may be a lot of potential state legislative candidates kicking themselves for not getting in the race," Hogan said.
