Dems face a steep climb in Ariz.

Democrats are brimming with optimism about their prospects in Arizona’s general election this year. There are grounds for such optimism. But in some cases, the evidence of a coming “blue wave” is being exaggerated.

Democrats haven’t won a statewide election in Arizona since 2008. The nadir was hit in 2014. The party fielded what was arguably the most highly qualified and impressive slate of candidates in Arizona history. And they all got shellacked, except for David Garcia, who was narrowly defeated for state superintendent.

The reason for the bleak streak has been the Republican registration and turnout advantage. In the past several general elections, Republicans have constituted more than 40 percent of those voting. With the rise of independent registrations, those who are still registered with one of the major parties are pretty brand-loyal. There used to be a lot of crossover voting in Arizona: rural Democrats voting for Republicans, urban Republicans voting for moderate Democrats. These days, not so much.

If Republicans are brand-loyal and more than 40 percent of the vote, a Republican candidate doesn’t have to do all that well with independents to get over the top.

The principal basis for Democratic optimism is the Trump effect. In elections across the country, President Donald Trump has been a turnout machine … for Democrats.

This manifested itself in Arizona in the special election to replace Rep. Trent Franks in a district with a lopsided Republican registration advantage. Democratic turnout rivaled Republican turnout. The independents went decisively for the Democratic candidate, Hiral Tipirneni. Some polls showed Tipirneni getting 15 percent of the GOP vote, suggesting that a Never-Trump Republican vote may be out there this year.

Republican Debbie Lesko eked out a win, but if those trends were to hold statewide in a general election, Democrats would be competitive in several races, most importantly for U.S. Senate and governor.

So far, so sound. But this is where the exaggeration starts to kick in.

The Democrats had a good quarter headed into the primary in terms of registering new voters, increasing their ranks by 21,000 compared to only 5,000 new GOP registrants.

But that needs to be put in context. Despite that surge, the Democratic registration disadvantage is actually greater than it was in 2016. Since Trump’s election, Democrats have added 20,000 registrants, while the Republicans have added nearly 25,000. In other words, prior to this recent surge, Democrats had actually been losing voters.

The more relevant point of comparison is 2014, an off-presidential year when most statewide offices were up for grabs. And there is some good news for Democrats: Compared with 2014, their registration disadvantage has shrunk from 178,000 voters then to 153,000 today.

But that’s still a big disadvantage. And the bad news is that the relative portion of the electorate registering as independent has actually receded. In 2014, registered independents outnumbered Republicans by 43,000. Today, Republicans outnumber independents by 45,000. So, Democrats need an even higher percentage of the independent vote to be competitive.

The recent Arizona primary is being cited as additional evidence of a coming blue wave. Democratic turnout set records in far more areas than did Republican turnout.

But, again, context is important. In the recent election, 117,000 more votes were cast in the Republican primary for governor than in the Democratic primary for governor, even though the Democrats had a far more competitive race.

Politics these days are scrambled. It is probable that Democrats will narrow the turnout disadvantage in Arizona this general election due to the Trump effect.

But it is unclear whether there will also be a surge in independent turnout, whether the independents will turn decisively toward Democrats in both federal and non-federal races, and whether there will be a Never-Trump crossover Republican vote.

Democrats need for all of those things to happen to win in an election that will undoubtedly still consist of far more Republican voters than Democratic ones.

Perhaps this is the best way to put it: Democrats have the best opportunity in a decade to climb the steep hill of the Republican registration and turnout advantage in Arizona. But it remains a very steep hill.