Washington (CNN) President Donald Trump thinks he's overdue some credit for steering the strongest economy on the planet -- and he's probably right.

"These numbers are very, very sustainable -- this isn't a one-time shot," Trump said on Friday, speaking from the South Lawn of the White House after news that the US economy grew at a 4.1% annual rate in the second quarter of the year.

Fresh from a trip to the Midwestern heartlands, the President is making the very best possible case for his administration as the pace heats up ahead of the midterm elections. He's belting out a strong economic message with a fervor that Democrats have yet to match this election cycle.

Presidents usually get too much blame when the economy is doing badly, since downturns are often caused by outside shocks or cyclical factors, but that also gives them a chance to crow when things are going full steam ahead.

Trump is not the kind of person to pass that up.

Often, the President's hyperbolic assessment of his own performance is at odds with the facts. But Friday's announcement that the economy grew at a 4.1% pace in the second quarter, the best showing since 2014, is genuine cause for celebration.

It may also be his best chance to argue that a huge and controversial tax cut, the only really significant legislation he has managed to pass, is -- as he said it would -- unleashing prosperity.

"We've never seen anything like (what) is going on right now," Trump told a hugely supportive crowd of steelworkers in Illinois on Thursday.

"GDP numbers will be announced tomorrow sometime. I don't know what they are, but I think they're going to be terrific," he added. "You know, when we took over it was really low, and it was heading lower, a lot lower. And it was going to be there fast. And great things have happened. So, whatever those numbers are, watch for them. Somebody actually predicted today, 5.3 (%). I don't think that's going to happen."

Looking for a boost

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The strong growth number gives the White House a significant boost after days of grim headlines, and its failure to move on from the President's humiliating summit performance with Russian President Vladimir Putin nearly two weeks ago.

It also offers some personal respite for Trump, given that he must feel that legal walls are closing around him, following news that one of his most important confidants, Allen Weisselberg, has been subpoenaed by federal prosecutors investigating his former lawyer Michael Cohen.

The New York Times reported on Thursday that special counsel Robert Mueller is examining Trump's tweets, potentially to see whether they can help him build a case that the President acted with malicious intent when he sacked former FBI Director James Comey.

Trump is forever trying to change the subject. With the current state of the economy, he may have some ammunition.

Unemployment is lower than it has been for decades, corporate earnings are strong and it seems unlikely that a sudden crisis is looming that could derail things before Americans head to the polls in midterm elections that will have a huge bearing on Trump's presidency.

Recent polls show that the economy is one of the few issues where Trump is approaching the kind of numbers that presidents conventionally need to win re-election.

Quinnipiac University poll conducted from July 18-23 showed that majorities of voters thought Trump had weakened the US abroad, was too close to Putin and lied about important issues. But a near majority -- 49% -- backed his handling of the economy.

Republican hopes of staving off a Democratic blue wave and boosting Trump's re-election prospects in 2020 may hinge on more voters deciding that for all the uproar and dislocation and falsehoods of the Trump presidency, he has made them more economically secure and given them a pay raise for which they have waited years.

GOP's best bet

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It's no exaggeration to say that the economy represents Trump's best argument heading into the fall. And Trump appears to be getting increasingly frustrated that the story is not being told.

Pointing at the press cameras during his trip to Illinois he complained: "They're dying to see us make a little bit of a mistake."

"Even though we've been here for a little more than a year and a half ... we really hit it big over the last six months," he said.

Trump can make a fair argument that he is not getting the credit he deserves on the economy, but he often has only himself to blame for it getting overlooked, given the daily political turmoil he creates.

And his White House displayed deepening concern in recent days about Trump country districts that sent him to the White House.

While the President claimed Thursday that his steel and aluminum subsidies on China and a clutch of US allies had revived the industry, his trade war threats appear to be having an alarming impact elsewhere.

The administratio n just unveiled a $12 billion aid program fo r farmers slammed by Chinese reprisals targeting Trump voters that are already having a painful impact on US soybean and pork exports.

The President also appeared to step back from the brink of a trade war with the European Union on Wednesday, basically agreeing to a deal to just start talking about tariff cuts.

"We just opened up Europe," Trump said in Dubuque, Iowa, earlier Thursday, misleadingly overstating the significance of his deal with Europe .

Key House and gubernatorial races in states that Trump won and will need again in 2020 are beginning to increasingly get bogged down in debate over the direction of Trump's trade policies. A set of NBC/Marist polls this w eek showed his approval rating down below 40% in Michigan and Wisconsin, which paved his way to the presidency.

There's also plenty of scope to quibble with the substance of Trump's economic claims. While growth may be roaring, critics say the tax cuts may not filter down significantly to blue-collar Americans and are certain to widen economic inequality.