WASHINGTON — A potential backlash from the new tax law and President Trump’s unpopularity in Democratic-leaning states could combine to turn swaths of blue America even bluer in this year’s elections, a development likely to deepen already intense polarization in Congress.

Recent retirement announcements of two senior House Republicans from California put control of their seats in jeopardy and, coupled with some recruiting failures, exacerbated Republican fears of steep midterm losses. The prospect of multiple Republican defeats in California as well as New York and New Jersey threatens to diminish the already thinning ranks of more centrist Republicans.

Democrats might cheer such an outcome. But the long-term result could be a Congress that is more insular, as well as an increase in situations such as the new tax law. In that case, Republicans squeezed revenue from states dominated by Democrats and returned the benefits to Republican strongholds elsewhere across the country.

If House delegations become more sharply divided by state, such geographic favoritism could become more prevalent because the majority party would have less incentive to consider the interests of states where they have little or no membership at political risk. The concern is that lawmakers would retreat even further into their ideological camps, staring warily across state lines.