The Trump administration's policies have largely favored his own party and hurt voters from blue states.

The base-oriented approach to policymaking and messaging could make future collaboration with Democrats all the more difficult

The president's appeals to the base may get his own supporters fired up, but they're also a rallying cry for Democrats in the upcoming midterm elections.

— President Trump's major policy moves over the course of his first year in office have had a common denominator: They either overtly favor his base of support — the roughly one-third of voters who solidly back him — or they appear to penalize those states that vote Democratic.

The most striking example is tax reform, which struck a blow against blue-state Americans who tend to pay high state and local taxes, or SALT. These are residents of states that did not vote for Mr. Trump in 2016, and beginning this year, SALT deductibility on federal taxes is curtailed.

Other recent policy moves also appear to have an anti-blue tilt. Soon after the Trump administration announced a plan to expand offshore drilling in federal waters, it granted a waiver to Florida — a crucial Trump state in 2016. Blue states are also eager for waivers, but they're still waiting.

Disaster relief funding has also sparked accusations of partisanship. Democratic politicians in heavily blue California were outraged in November when a Trump administration disaster aid request to Congress did not specifically mention their state, following devastating wildfires. A December aid request, which does mention California (as well as Texas, Florida, and Puerto Rico), passed the House but languished in the Senate.

Puerto Rico, too, a Democrat-dominant US territory (albeit with a Republican governor) has also complained bitterly about its treatment by Washington following hurricane Maria.

Marijuana is another case in point. A recent Justice Department memo freed prosecutors to enforce federal law more aggressively in states that have decriminalized marijuana's production and sale — mostly blue states, including California.

Even the Trump administration's recent letter casting doubt on federal funding for a new rail tunnel between New York and New Jersey has political overtones. Both states are solid blue.

Trump's base-oriented approach to policymaking and messaging could make future collaboration with Democrats all the more difficult as soon as Friday, when the government will shut down if a funding deal in Congress can't be reached. The clock is ticking, too, on the young illegal immigrants who face deportation if Congress can't agree on a plan by March 5.

And the November midterms are fast approaching. Trump's appeals to the base may get his own supporters fired up, but they're also a rallying cry for Democrats, who have a shot at retaking the House and possibly even the Senate. If Republicans lose either house, Trump's ability to get anything through Congress will be severely curtailed.

To the winner go the spoils

Republican presidential nominee Donald Trump walks to the stage at a campaign rally in Pensacola, Florida, U.S., September 9, 2016. REUTERS/Mike Segar Republicans say it stands to reason that Trump-era policies would favor his own party: To the winners go the spoils.

"In a polarized environment, where only Democrats before 2010 [during President Obama's first two years] and only Republicans since 2016 are making policy, there's a natural tendency to have policy favor the people who are making it," says Republican pollster Whit Ayres.

"Democrats have that tendency as well," Mr. Ayres adds, pointing to the Obama administration's unwillingness to grant waivers on some requirements of its signature health-care reform law. "I don't know that it's a conscious choice, as much as it is a logical consequence of having one party in power."

Other observers see a more profound shift at work. Partisan polarization, which has been deepening for decades, is certainly a factor. But Trump's approach to politics is unlike anything the nation has seen before.

Trump didn't follow the usual path of a successful presidential candidate, who plays to his party's base to win the nomination, then tacks to the center for the general election. Rather, Trump has rarely veered from his base approach. His convention speech emphasized populist, nativist themes, as did his inaugural address — not the high-road, unifying rhetoric that Americans expect at such national moments.

As president, Trump still aims most of his messaging at his base. It's possible, some observers suggest, that his reported vulgar comment about immigrants from Haiti, El Salvador, and Africa was an intentional signal to conservative TV talkers like Tucker Carlson and Ann Coulter that he hadn't gone soft on immigration.

In addition, aside from regular travel to the blue states where he has residences, New York and New Jersey, Trump travels for events almost exclusively in states that he won in the 2016 election. He has yet to travel to California, a rarity for the first year of a presidency in recent decades.

"This is not a 'so what,' or 'all presidents do this,' " says Jeremy Mayer, an associate professor of policy and government at George Mason University in Arlington, Va. "All presidents don't do this. If they did, then Democratic presidents would never have visited the South, and would have designed their policies to damage the South."

President Donald Trump waves as he walks toward Air Force One at Morristown Municipal Airport in Morristown, N.J., Sunday, Oct. 1, 2017. AP Photo/Susan Walsh

The end of congressional bargaining

On tax reform, the most significant legislative achievement of Trump's first year, it's probably not fair to point just at Trump for a policy that tends to pose more harm to Democratic constituencies than Republican.

"It's more the Republican congressional majorities that have been developing these programs in their detail," says Cal Jillson, a political scientist at Southern Methodist University in Dallas.

"What has changed is that while there used to be a modicum of congressional bargaining across major policy developments, the party in power now tries to pass legislation on straight party-line votes," says Mr. Jillson. "In that case, you can both enact your traditional policy preferences without compromise, and enjoy punishing your enemies."

It's true that Mr. Obama also passed major legislation with just Democratic votes, but not before making major concessions to Republicans, Jillson notes.

In the first two years, "Obama and the Democratic majorities bent over backwards to develop the Mitt Romney version of national health care and also to give a third of the stimulus package to tax cuts," Jillson says. "That, I think, was the end of the traditional attempt to offer elements of a major package to your opponents, to try to get them on board."

Tax reform, and the new limit on the SALT deduction, presented an interesting case for Trump. As a native of New York, a high-tax blue state, he might have taken pity on those facing a financial blow. But New Yorkers aren't his base. The state didn't vote for him in 2016, and when some of his wealthy hometown friends pushed him last month to help on SALT deductibility, he joked, "You guys seem to be doing OK," according to The New York Times.