With primary season concluded, likely presidential nominees Donald Trump and Hillary Clinton have accelerated their spending on promotional products in anticipation of a general election showdown this November. Trump continues to significantly outpace his potential opponent, spending $6.8 million on branded merchandise compared to $1.6 million for Clinton.

After lavishly spending on “collateral” in late 2015 and early 2016, Trump has escalated his spending after seizing the lead in the Republican primary. The candidate spent $3.3 million on promotional products from March through May – nearly equal to what he had spent on merchandise for the entirety of the election prior.

Clinton has also increased her promo spending after emerging as the favorite in the Democratic primary. After spending just $38,000 on merchandise in February, Clinton spent $280,000 the following three months while doubling her amounts each month. Clinton spent significantly on promo products in 2015 (over $1 million dollars) but had eased her spending early in 2016.

The depth of Trump’s reliance on promotional products goes beyond mere totals. The likely Republican nominee has spent 10.4% of his total expenditures on collateral, while Clinton’s total makes up just 0.8% of her total spending.

Trump’s heavy investment in promotional products is just one hallmark of his unusual campaign strategy. The Republican has mostly eschewed donations, relied heavily on free media coverage and has otherwise spent sparingly. The strategy has prompted many campaign experts to question Trump’s ability to wage an effective general election campaign. “Trump’s failure to develop an effective fundraising operation has his campaign at this point without the resources to scale up its staffing, build a field organization or begin advertising in crucial states,” Anthony Corrado, a professor of government at Colby College and campaign finance expert, told CNBC.

However, despite his significant spending on campaign paraphernalia, Trump has not been the biggest promotional spender this election. That title belongs to Democrat Bernie Sanders, who has spent over $9 million on promotional products. However, the Vermont Senator spent $285,000 on promo items in May, a 60% reduction of his previous month’s spending in a sign that his campaign had lost momentum.

While Sanders has outspent Trump on promotional products, branded items represent only 4.1% of Sanders’ total spending, showing that Trump has relied on promotional products much more heavily in relation to his total spending.

Trump has primarily used Ace Specialties (asi/103533), a Lafayette, LA-based distributor, for his branded items. Trump’s campaign has also used custom headwear maker Cali-Fame as well as Maxim Advertising, a distributor based in Newton, IA. Clinton has exclusively used Financial Innovations (asi/194037), a Cranston, RI-based distributor that specializes in Made in America products and Democratic political candidates. While the spending by Trump and Sanders is extremely elevated, it falls in line with an increasing emphasis by presidential candidates to use promotional products to elicit campaign contributions, mobilize volunteers and raise awareness. Through merchandise sales, President Barack Obama raised $77 million in his two elections. Reuters reported last month that Sanders had sold 800,000 individual items and raised $12.8 million, while Trump had raised $6 million in contributions from campaign merchandise sales. For Trump, the sum represented the majority of his campaign contributions. “The sale of official campaign products has been extremely successful,” Trump Spokesperson Hope Hicks told Reuters.

ASI has been regularly conducting its Presidential Promo Poll, which gauges the role of promotional products and branding in predicting the results of this year’s election. Every two weeks, 400 American consumers are asked a single question: If you received a bumper sticker from Trump and Clinton, which one would you be most willing to put on your car? In the latest poll, the two candidates were locked in a dead heat.