Labor Day is a celebration of the American worker, as well as a farewell to summer.

It also marks the time when political campaigns kick into high gear for the two-month sprint to Election Day. Get ready for television ads, campaign mailers, phone calls and text messages.

And to mark the holiday in North Texas, incumbent Republican Sen. Ted Cruz is headlining a Collin County GOP rally in McKinney with Gov. Greg Abbott, Attorney General Ken Paxton and other candidates. Similarly, the Dallas County Democrats are hosting their annual Labor Day picnic with dozens of candidates and their supporters.

We're officially in campaign mode.

The biggest question heading into the November midterms is whether there will be a so-called blue wave of Democratic wins. It's difficult to say because the contests will hinge on turnout, and no one knows how many Democrats will show up at the polls, locally or statewide.

Texas is still considered a solid Republican state, but the urban areas are Democratic Party strongholds with the potential of swinging regional elections.

Here are three other questions that will be answered Nov. 6.

Can Beto O'Rourke develop a winning coalition of Texas voters?

Criminal justice reform activists from throughout Texas commemorate the 55th Anniversary of the historic March on Washington with a Rally for Justice and Equality on the south steps of the State Capitol Aug. 28, 2018. The march and rally featured special guests including Rep. Beto O'Rourke, a candidate for U.S. Senate. (Ralph Barrera / Austin American-Statesman)

The El Paso congressman has staged a remarkable Senate campaign, giving Texas Democrats hope that the party can notch its first statewide win since 1994. He's raising more money than Cruz, attracting enormous crowds and running close to him in most polls.

But the math isn't on O'Rourke's side. In most Texas midterm elections, far more Republicans vote than Democrats. Consider that the Texas Organizing Project, a progressive group committed to criminal justice reform, estimates that there are 850,000 more Republicans in the Texas electorate than Democrats.

That means O'Rourke will have to persuade a significant number of Republicans to abandon their party and vote for him. He also has to get more Democrats and independent voters to the polls.

There's some evidence that President Donald Trump's supporters aren't sold on Cruz, who famously clashed with the New York businessman during the 2016 GOP presidential primary. The danger for Cruz is if those voters stay home, or skip voting in his race.

Sen. Ted Cruz gives an election speech at Lava Cantina in The Colony on Aug. 27, 2018. (Nathan Hunsinger / Staff Photographer)

To truly make 2018 a wave election, Democrats will need to register more new voters to dent the GOP's structural advantage in statewide contests. And though O'Rourke and his supporters want to win, if he finishes within 10 percentage points of Cruz, it would pave the way for future Democratic Party victories.

Can Democrats pick up at least three congressional seats?

Texas Republican Reps. Pete Sessions of Dallas, John Culberson of Houston and Will Hurd of San Antonio all face tough re-election bids.

Democrats Lizzie Pannill Fletcher and Gina Ortiz Jones are trying to reach progressive voters to unseat Culberson and Hurd, respectively. But the most watched and perhaps most expensive race is in Sessions' northeast Dallas County district, where he's trying to stave off a spirited challenge from Dallas lawyer Colin Allred.

Dallas Democrat Colin Allred is running against Republican Rep. Pete Sessions. (Photos by Andy Jacobsohn/The Dallas Morning News)

Allred, a former NFL player, is a progressive candidate who touts giving all Americans access to Medicare, stricter background checks for gun buyers and more money for public education. He has a formidable grass-roots army that will knock on doors in a district Hillary Clinton won in the 2016 presidential race.

Allred has criticized Sessions for voting in favor of tax cuts that favor the rich and for not supporting the Affordable Care Act. He'll also try to make the race a referendum on Trump and his policies. Sessions is casting Allred as a liberal who would advance the agenda of House Minority Leader Nancy Pelosi.

Texas lawmakers created the district map to include a majority of Republicans, so Sessions has an advantage. But both campaigns are targeting the district's suburban women, and though Trump did well with white women voters in 2016, Allred hopes he can convince them that Trump, and by association Sessions, don't support policies that would help them and their families.

Can Republicans hold several North Texas legislative seats?

The Texas Legislature's most competitive contests will play out in Dallas-Fort Worth.

Dallas Republican Sen. Don Huffines is defending his seat in a district that leans Republican, but with so much Democratic activity in the county, Dallas lawyer Nathan Johnson believes he can ride a blue wave into the Senate.

Burleson Democrat Beverly Powell has the same aspiration in Sen. Konni Burton's Tarrant County district. Democrat Wendy Davis represented it until giving up the seat to run for governor in 2014 against Greg Abbott.

Davis won the seat in presidential years, when Democratic turnout is higher. Powell has to hope for an uptick in voters from her party, as well as support from moderate Republicans who don't like Burton's brand of conservatism.

Nearly all of the state's competitive House races are in Dallas County, with Republicans trying to defend districts Clinton won in 2016.

Democrats have one district to defend — the one held by Rep. Victoria Neave, who defeated Republican Kenneth Sheets to win the seat in 2016.