I hope the Democrats win the House and the Senate in 2018 but there are problems. For example the liberal extremists could screw up everything. Another problem for the Democrats is the American economy which is fantastic these days. Anyone who wants a job can get a job thanks to the tax reform bill and thanks to throwing out unnecessary regulations, in other words thanks to the Republicans. We will see what happens.

Wall Street Journal - Democrats’ Path to a November Majority Has Hurdles. Strong economic news and polling on GOP tax cut could impede the blue wave.

By Gerald F. Seib - Updated March 12, 2018

Democrats figure to have a good day Tuesday in Pennsylvania. They’ll either win or come close to winning a special election for an open House seat, in a district that President Donald Trump carried by 20 percentage points and that should be a lock for the Republicans.

Democrats will take that as a sign that they are well-positioned to win back control of the House this year, and maybe the Senate, because they have well-funded candidates, a party base highly motivated by disdain for the president, and a key constituency in suburban women moving their way. That’s all true.

But November’s midterm elections are eight months away, a lifetime in modern politics. And as they ride into the sunset Tuesday, Democrats also ought to be concerned about some warning signs out on the horizon. Here are a few:

The economy. It’s in great shape, which is the best available news for Mr. Trump and his Republicans. A leading indicator of that trend line came in the February jobs report released last Friday, the import of which may have been lost amid the kaleidoscope of other news swirling around Washington.

It was a blockbuster report: The economy added 313,000 jobs in February, the largest gain in more than a year. More than 800,000 Americans got off the sidelines and entered the workforce, the largest one-month jump since 1983. Wages rose some, but not a lot, suggesting an economy that can run strong without overheating.

The yawning budget deficit that will be opened up by the tax cut Congress passed late last year—and the potential trade war the Trump administration may be starting—have the potential to do serious damage. But those risks are a ways off. For now, things look good, which is not so good for Democrats.

Tax-cut popularity. Americans appear to be warming up to that tax cut, which wasn’t exactly met with a wave of popular support when first passed.

In the RealClearPolitics average of national polls, approval of the tax cut has risen to 42% from 30% at the end of last year. The share disapproving of the law still tops the share that approves, but only by 3 percentage points. For congressional Republicans who needed something of their own to run on, the trend line is moving in the right direction.

Democrats’ own untested economic message. The flip side of warmer feelings toward the tax cut is the Democrats’ struggle to hone a message to counter it. They started down that path last week with a plan that would unwind much of the tax-cut package to raise funds for a $1 trillion investment in American infrastructure.

Infrastructure spending is a job creator and popular with both business and unions, so that’s a good message. Still, it puts Democrats in the awkward position of campaigning on a tax increase, including a higher top tax rate and a return of a broad alternative minimum tax. They may find a more potent message is one that says the tax cut is unfair to average Americans because the big deficits it will generate will force cuts in Medicare.

Signs of Republican enthusiasm. Democrats feel good because they have a fired-up base, thanks in large part to Mr. Trump. But Republicans are starting to see some signs that their own base, discouraged six months ago because of failures in Washington, is coming to life as well.

The clearest signals came in Texas’ primary election last week. Republicans showed up in big numbers at a time Democrats thought they had the enthusiasm edge in the traditionally red state. In the U.S. Senate primary, for example, more than 60% of the votes cast were by Republicans, compared with 37% for Democrats, even as Democratic turnout was up more than 80% over the last midterm primary, in 2014.

A cultural disconnect in key places. The good news for Democrats is that their liberal base is highly motivated. The bad news is that the base may block more centrist candidates who would have a better shot at winning in November in culturally conservative states.

A party driven by its liberal base may face particular problems in the fight for control of the Senate, where Democrats this year will need to win in several states that Mr. Trump carried. “In the Senate, they have to navigate constituencies that are fundamentally opposed to their view of cultural issues like guns and immigration,” says Josh Holmes, former chief of staff to Senate GOP leader Mitch McConnell. “In short, the catalysts underpinning all of the Democratic energy nationwide simultaneously create huge liabilities in the states that matter in 2018.”

Write to Gerald F. Seib at jerry.seib@wsj.com

Appeared in the March 13, 2018, print edition as 'Democrats Are Fired Up, but Hurdles Loom.'